1. Field of the Invention
This invention relates to wrenches for bolts and nuts and more particularly to back-up wrenches used for threaded connectors on flanged connections.
2. Description of Related Prior Art
The use of flanged connections on pipes, drilling tools, etc., is widespread. When two flanges are secured to each other, for example, with through stud bolts, it is necessary to use a nut on each threaded end portion of the stud. Normally, a first nut is first screwed into position on the stud and the stud is then placed through a flange hole. A second nut is then placed onto the opposite threaded end and turned to bear on the face of the flange in order to tighten the flanged connection and form a seal. Often, when turning the second nut, because of existing frictional forces, the stud with the first nut will start rotating, thereby preventing the completion of the nut-tightening operation. Such an operation may often require two operators, but when another operator is unavailable, or when space precludes the use of two operators, special nut and bolt holding devices, known as "back-up" wrenches, are used. To prevent the bolt from rotating, the back-up wrench is placed on the first nut and allowed to bear against and be supported by the next adjacent nut.
Recently, power operated wrenches have been introduced on the market for tightening flanged bolts and nuts. These power tools generate very high torques compared to manual wrenches. Such torques often force a back-up wrench very hard against the adjacent nut which supports and provides the required reaction force to the back-up wrench. After the completion of such a nut or bolt tightening operation, the removal of a conventional back-up wrench is made possible with the aid of a heavy hammer striking a hard blow to the wrench or with the aid of a long pry bar prying the back-up wrench loose from its forced seating against said adjacent nut. In contradistinction, the back-up wrench of this invention can be easily removed, even when placed under great load, by simply pulling on a release lever.